Henrietta Swan Leavitt - Measuring the Stars
Astronomer
Born: July 4, 1868, Lancaster, Massachusetts, U.S.A.
Died: December 12, 1921, Cambridge, Massachusetts, U.S.A.
Henrietta Leavitt was a brilliant and determined astronomer whose groundbreaking discovery allowed humanity to understand the true scale of the universe.
Leavitt was born on July 4, 1868, in Cambridge, Massachusetts. She was the daughter of a Congregational minister and grew up in a time when few women were encouraged to pursue science. At first, she studied art and music at Oberlin College. Later, she transferred to the Society for the Collegiate Instruction of Women, which later became Radcliffe College. It was there, in her final year, that she took an astronomy course and discovered her lifelong passion for studying the stars.
After graduating in 1892, Leavitt became very sick with an illness that left her severely deaf. Even though her health slowed her down, she never lost interest in astronomy. In 1895, she began volunteering at the Harvard College Observatory. The observatory’s director, Edward Pickering, had gathered a group of women to work as “computers.” These women studied photographs of stars and recorded their brightness, colors, and positions. At the time, women were not allowed to use telescopes or lead research projects. They were paid very little, usually around 25 cents an hour. Because of Leavitt’s excellent work, she was eventually promoted to a permanent position and earned 30 cents an hour.
Leavitt was placed in charge of studying variable stars. These are stars that do not shine at a constant brightness but instead become brighter and dimmer over time. Her job required her to compare thousands of photographic glass plates of the night sky, sometimes taken years apart, to find even the smallest change in a star’s light. It was slow and detailed work, but Leavitt had a sharp eye for patterns. Over the course of her career, she discovered more than 2,400 variable stars, about half of all those known in her time.
Her most important contribution came in 1908, when she made a groundbreaking discovery about Cepheid stars. Cepheids are a special kind of variable star. Leavitt noticed that the longer it took a Cepheid star to go from bright to dim and back again, the brighter the star actually was. This pattern became known as the period-luminosity relationship. Her discovery meant that astronomers could now calculate the distance to faraway stars and galaxies by measuring how long their light cycles lasted.
Leavitt’s work transformed astronomy. Using her discovery, astronomer Edwin Hubble was able to prove that the universe is expanding. His famous Hubble’s Law was only possible because of the foundation she had laid. In fact, when NASA launched the Hubble Space Telescope in 1990, its very mission, to explore deep space, was made possible by Leavitt’s work decades earlier.
In addition to her work with Cepheid stars, Leavitt developed a standard system of measuring the brightness of stars using photographic plates. This became known as the “Harvard Standard” and was adopted internationally in 1913. Her careful observations and methods gave astronomers reliable tools they still use today.
Sadly, Leavitt never received the recognition she deserved during her lifetime. Because of gender bias at the time, women like her were not given credit equal to their male colleagues. Although she was nominated for the Nobel Prize in Physics in 1925, she had already passed away in 1921 at the age of 53 from cancer. Many people believe she should have been awarded the prize while she was alive.
Even with her health struggles and hearing loss, Leavitt never stopped working when she was able. A colleague once said she had “the best mind at the Observatory.” Today, she is remembered as one of the most important women in astronomy. Her name lives on through the asteroid 5383 Leavitt and a crater on the Moon named in her honor.
Henrietta Swan Leavitt showed that persistence and curiosity can change the world. Her discovery of the period-luminosity law continues to guide astronomers as they measure and understand the universe. Though her life was short, her impact on science was immeasurable.
SOURCES:
“Infoguides: Deaf People in Astronomy and Rocket Science: Henrietta Swan Leavitt.” Henrietta Swan Leavitt - Deaf People in Astronomy and Rocket Science - InfoGuides at Rochester Institute of Technology, infoguides.rit.edu/deafstars/leavitt.
“Remembering Astronomer Henrietta Swan Leavitt.” Center for Astrophysics | Harvard & Smithsonian, www.cfa.harvard.edu/news/remembering-astronomer-henrietta-swan-leavitt.
“A Science Odyssey: People and Discoveries: Henrietta Leavitt.” PBS, Public Broadcasting Service, www.pbs.org/wgbh/aso/databank/entries/baleav.html.
Keywords: Science, Innovation, Perseverance, Courage, Responsibility, Selflessness, Make a Difference, Face Prejudice

Image Citation: Public Domain